CI: add Vale to apply Google style guide to all md files

.circleci/config.yml

@@ -68,6 +68,13 @@ jobs:
             wget https://raw.githubusercontent.com/CharLotteiu/pingcap-docs-checks/main/check-manual-line-breaks.py
             python3 check-manual-line-breaks.py $(git diff-tree --name-only --no-commit-id -r upstream/master..HEAD -- '*.md' ':(exclude).github/*')
 
+      - run:
+          name: "Vale linter"
+          command: |
+            sudo curl -sfL https://install.goreleaser.com/github.com/ValeLint/vale.sh | sh -s latest
+            export PATH="./bin:$PATH"
+            vale $(git diff-tree --name-only --no-commit-id -r upstream/master..HEAD -- '*.md' ':(exclude).github/*')
+
   build:
     docker:
       - image: andelf/doc-build:0.1.9

.vale.ini

@@ -0,0 +1,5 @@
+StylesPath = styles
+MinAlertLevel = error
+
+[*.md]
+BasedOnStyles = Google, PingCAP

a-test.md

@@ -0,0 +1,19 @@
+---
+title: Distinct Optimization
+summary: Introduce the `distinct` optimization in the TiDB query optimizer.
+---
+
+# Migrate from Azure to TiDB
+
+This document introduces the `distinct` optimization in the TiDB query optimizer, including `SELECT DISTINCT` and `DISTINCT` in the aggregate functions.
+
+## Distinct Optimize
+
+The `DISTINCT` modifier specifies removal of duplicate rows from the result set. `SELECT DISTINCT` is transformed to `GROUP BY`, for example：
+
+* Check whether the TiKV process is normal, the network is isolated, and the load is too high, and recover the service as much as possible.
+* This document introduces its concept, implementation principles, auto-increment related features and restrictions.
+
+### Distinct Data
+
+The value of this parameter should be between 7 - 10 in github.